1. Field of the Invention
The present invention relates to an original reading apparatus and an information processing apparatus having such an original reading apparatus, and more particularly it relates to an information processing apparatus such as a facsimile, an image reader, a digital copying machine, an electronic black board and the like having a reading apparatus as an input portion for reading information on an original to be read while relatively shifting the original in a condition that the original is closely contacted (including light contact) with an original reading surface.
2. Related Background Art
Recently, in order to make information processing apparatuses such as facsimiles, image readers and the like compact and to improve the performance of such information processing apparatuses, there has been proposed an elongated line-sensor which can be used with an equi-magnification optical system as a photoelectric conversion device for a reading apparatus or which can be used without any specific optical system. Particularly, reading apparatuses wherein reflection light including information from an original can be directly detected by a photoelectric conversion device through a transparent spacer such as glass without using an equi-magnification fiber lens array, thereby making the apparatus compact and inexpensive have been put to practical use.
Incidentally, hereinafter, an optical conversion apparatus of the type wherein information is read without any optical system is referred to as "image sensor of complete contact type". FIG. 24 is a schematic sectional view of a reading apparatus of a conventional facsimile system in which an image sensor of complete contact type is used as an image information reading apparatus and which includes an original separation roller and a contact sensor roller (CS roller) as a convey means.
A flow of an original in FIG. 24 is as follows. When an original bundle 103 is inserted from an original insertion opening 101 into an original insertion path 102, a signal from an original presence/absence detection sensor (not shown) is sent to a control portion so that an original presence condition is ascertained by the apparatus. Further, the original bundle 103 is inserted to reach an original separation portion 106 which includes an original separation roller 104, and an original separation piece 105 opposed to the original separation roller 104 with the interposition of an original convey path and biased toward the original separation roller 104 by a biasing means (not shown).
Then, when a start key (not shown) arranged on an operation portion is depressed, a reading drive system (not shown) is operated so that the original separation roller 104 is rotated to convey the original bundle 103. The original bundle 103 is pinched between the rotating original separation roller 104 and the original separation piece 105 urged against the separation roller 104 by the biasing force, thereby separating the original one by one. The separated original 107 is conveyed by the rotating original separation roller 104, with the result that a tip end of the original is detected by an original tip end sensor (not shown). The original 107 is further conveyed by the rotating original separation roller 104 to reach an image information reading portion 110 which includes an image sensor 108 of complete contact type, and a CS roller 109 opposed to the image sensor 108 with the interposition of the original convey path. The image sensor 108 of complete contact type is urged against the CS roller 109 by a biasing means 111. Image information on the original 107 sent to the image information reading portion 110 is read by the image sensor 108 of complete contact type while the original is being conveyed by the rotating CS roller 109.
By the way, during the reading of the image information, if an original convey speed is not constant, the image information cannot be read properly. However, since the original convey speed of the original separation roller 104 is not constant (uneven), the original convey speed is determined by the CS roller 109. That is to say, the original convey speed of the CS roller 109 is set to be greater than that of the original separation roller 104, and an original convey force of the CS roller 109 is set to be sufficiently greater than a friction force between the original 107 and the original separation piece 105.
In this way, the original 107 is conveyed by the CS roller 109 while reading the image information by means of the image sensor 108 of a complete contact type. When a trailing end of the original is detected by an original trail end detection sensor (not shown), the original is discharged out of the apparatus through an original discharge opening 112.
As mentioned above, since the original convey speed of the original separation roller 104 is not constant (uneven), even when the tip end of the original is detected by the original tip end detection sensor after the original has been separated, the time period for conveying the original from the original tip end detection sensor to the image information reading portion does not become constant, thereby causing a problem that an excessive or poor margin is created at a tip end portion of the original.
Further, as shown in FIG. 25, if the original is skew-inserted, either the left or right side (left side in FIG. 25) of the tip end of the original 107 will firstly be abutted against the CS roller 109. In this case, since the left side of the original 107 is conveyed by the CS roller 109, the left side of the original is subjected to the original convey force. On the other hand, since the original convey speed of the original separation roller 104 is smaller than that of the CS roller 109, a central portion of the original is subjected to a friction force (between the original 107 and the original separation piece 105) directing toward a direction opposite to the original convey direction. As a result, as shown in FIG. 25, a moment is generated in the original 107 to rotate the original in an anti-clockwise direction, thereby enhancing the skew-feed of the original.